CN1722560A - Overcurrent protection circuit - Google Patents
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- CN1722560A CN1722560A CN 200510084805 CN200510084805A CN1722560A CN 1722560 A CN1722560 A CN 1722560A CN 200510084805 CN200510084805 CN 200510084805 CN 200510084805 A CN200510084805 A CN 200510084805A CN 1722560 A CN1722560 A CN 1722560A
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Abstract
The invention provides an over-current protection circuit which can rapidly detect the over-current status without damaging the stability of a circuit and implement the current limit and a voltage regulator using the over-current protection circuit. A voltage generation circuit (100) includes the regulator (10), a first detecting circuit (20) and a second detecting circuit (30). The first detecting circuit (20) includes a first transistor (22), a first resistance (R1) and an error amplifier (24). The second detecting circuit (30) includes a second transistor (32), a second resistance (R2) and a detecting transistor (34). When an output current (Iout) exceeds a detecting threshold current, the detecting transistor (34) is turned on for the feedback of the limitation of the output current on an operational amplifier (12). The detecting threshold current of the first detecting circuit (20) is arranged to be higher than the detecting threshold current of the second detecting circuit (30), and the detecting action speed is also arranged to be faster than the detecting action speed of the first detecting circuit (20).
Description
Technical field
The present invention relates to current foldback circuit, particularly to circuit protection technology as the overcurrent of the voltage generation circuit of power circuit.
Background technology
In making the stable adjuster of voltage etc., with power MOSFET (Metal OxideSemiconductor Field Effect Transistor), IGBT (insulated gate bipolar transistor), bipolar power transistor etc. as output transistor.These transistors, as maximum permissible current, the current value that flows through with to common action the time has enough surpluses and designs.
, though like this having under the situation that enough design margins design, in situation that the output loading circuit is short-circuited etc., the overcurrent that surpasses maximum permissible current flows through transistor, still has the problem that its reliability is exerted an influence.In addition,, but be connected to transistorized load circuit, the situation of carrying out the electric current restriction is arranged in order to protect even below transistorized maximum permissible current.
Therefore, avoided overcurrent for protective transistor in the past, or be limited in the electric current that flows through in the load circuit, setting has the protective circuit (patent documentation 1) of current limit function in adjuster.
[patent documentation 1] spy opens flat 5-315852 communique
,, detect the electric current in transistor, flow through and protective circuit, the problem that exists the stability to circuit to exert an influence with current limit function of feedback as also pointing out in the above-mentioned document.That is, in order to improve the tracing property of the change of output current and enlarge under the situation of frequency band of feedback loop, the stability of circuit is compromised, the problem that exists circuit to vibrate easily.On the contrary, reduce the gain of feedback loop in the stability of priority circuit and frequency band is narrowed down, form under the situation of the circuit that is difficult for producing vibration, can not follow the tracks of the rapid variation of output current, need the time to apply the electric current restriction, and have the problem that flows through big electric current during this period.That is, in having the protective circuit of current limit function, there are the relation of balance (trade-off) in the stability of circuit and detection responsiveness.
Summary of the invention
The present invention is the invention in view of above-mentioned problem, and its purpose is to provide a kind of stability of not damaging circuit and detection of excessive current and carry out the current foldback circuit of electric current restriction and use its voltage generation circuit promptly.
In order to solve above-mentioned problem; the current foldback circuit of the present invention's one scheme; the situation to be output as over-current state from voltage generation circuit that comprises detects by the supervision electric current corresponding with the output current of this voltage generation circuit, and the 1st testing circuit, the 2nd testing circuit of restriction output current.In this current foldback circuit; make the detection quick action of the detection responsiveness of the 2nd testing circuit than the 1st testing circuit; and, must be than the detection threshold electric current height of the over-current state of the 1st testing circuit with the detection threshold current settings of the over-current state of the 2nd testing circuit.
According to this scheme, output current is with under the rapid situation about rising of the speed that can not follow the tracks of in the 1st testing circuit of preferential design stability, carry out the electric current restriction by responsiveness than the 2nd testing circuit of stable preferential setting, then, after output current was littler than the detection threshold electric current of the 2nd testing circuit, only the 1st testing circuit carried out the electric current limit movement.Its result, become unstable at the 2nd testing circuit, produce the electric current restriction that switches to the 1st testing circuit before vibrating, even or the generation vibration also switches to the electric current restriction of the 1st testing circuit with the very short time, so do not damage the stability of circuit, can limit the rising of rapid output current.
At least one of the detection threshold electric current of the 1st testing circuit and the 2nd testing circuit is set lowly in the time of also can hanging down at the output voltage of voltage generation circuit.When output voltage is low, promptly when the load circuit short circuit,, in output current and output voltage characteristic, can obtain so-called Off word characteristic by setting the limits value of output current low, can suitably suppress the heating of circuit.
The 1st testing circuit, the 2nd testing circuit also can be connected in parallel with described voltage generation circuit respectively and will flow through the resistance that a terminal potential is fixed with the corresponding electric current of output current and be transformed to voltage, detect over-current state by relatively more corresponding voltage with separately detection threshold electric current, the 1st testing circuit comes comparative voltage by voltage comparator, limit the feedback of described output current, the 2nd testing circuit will be input to by the voltage of described resistance conversion and detect transistorized control terminal, and with detect the corresponding over-current state that detects of transistorized conduction and cut-off action, the electric current that flows through during according to conducting limits the feedback of described output current.
' transistorized control terminal ' refers to terminal that transistorized conduction and cut-off is controlled, at FET middle finger gate terminal, at bipolar transistor middle finger base terminal.
Another program of the present invention is a voltage generation circuit.This voltage generation circuit comprises: comprise output transistor and the adjuster circuit of operational amplifier that output transistor is controlled; And the 1st testing circuit, the 2nd testing circuit.The 1st testing circuit comprises: the 1st transistor that is arranged in parallel with output transistor; The 1st resistance on the 1st transistorized current path is fixed and be arranged on to the voltage of one end; And the voltage that presents on the other end of comparison the 1st resistance and the voltage of the 1st detection threshold electric current correspondence, when the voltage that presents is high, operational amplifier is limited the error amplifier of the feedback of output current on the other end of the 1st resistance.The 2nd testing circuit comprises: the 2nd transistor that is arranged in parallel with output transistor; The 2nd resistance on the 2nd transistorized current path is fixed and be arranged on to the voltage of one end; And the voltage that presents on the other end with the 2nd resistance is input to control terminal, with the corresponding over-current state that detects of its conduction and cut-off action, and operational amplifier limited the detection transistor of the feedback of output current when detecting over-current state.Must be with the detection threshold current settings of the 2nd testing circuit than the detection threshold electric current height of the 1st testing circuit.
According to this scheme, the feedback that the over-current state of the output transistor that the 2nd testing circuit by at a high speed and stable two testing circuits of the 1st testing circuit detect adjuster circuit and carrying out limits electric current can not damaged the stability of circuit and detects, drives restriction at high speed.
The 1st testing circuit also can comprise a end that the current potential that is set at described the 1st resistance is fixing and the 3rd resistance between earthing potential and with the switching transistor of described the 3rd resistance bypass.On the control terminal of switching transistor, also can apply the output voltage of voltage generation circuit.
When switching transistor was switched on, promptly when output voltage was higher than threshold voltage, the 3rd resistance was by bypass, so electric current only is transformed to voltage by the 1st resistance.On the contrary, when output voltage was lower than the threshold voltage of the grid of switching transistor, switching transistor ended, and carries out current-voltage conversion so the 1st resistance and the 3rd resistance are connected directly.According to this scheme, according to output voltage, substantially regulate the detection threshold electric current, so when output voltage is low, promptly when the load circuit short circuit, by setting the limits value of output current low, in output current and output voltage characteristic, so-called Off word characteristic can be obtained, the heating of circuit can be suitably suppressed.
Similarly, the 2nd testing circuit can also comprise end that the current potential that is set at described the 2nd resistance is fixing and the 4th resistance between earthing potential, and, on the control terminal of switching transistor, also can apply the output voltage of voltage generation circuit with the switching transistor of described the 4th resistance bypass.
Be noted that the combination in any of said structure parts or arrange again etc. all is effectively, and comprised by embodiment of the present invention.
In addition, summary of the invention of the present invention needn't be discussed all essential feature, so that the present invention also can have the sub-portfolio that these discuss feature.
Description of drawings
Fig. 1 is the circuit diagram of the voltage generation circuit of expression embodiment of the present invention.
Fig. 2 (a), Fig. 2 (b) are the figure of the time waveform of voltage, electric current under the situation of load circuit short circuit of the expression voltage generation circuit that is connected to Fig. 1.
Fig. 3 is illustrated in the 1st testing circuit, is used to set the circuit diagram of the structure of the detection threshold electric current corresponding with output voltage.
Fig. 4 is the block diagram of structure of the electronic installation of the expression voltage generation circuit that loaded Fig. 1.
Embodiment
Below, according to preferred implementation the present invention being described, these preferred implementations are not to limit scope of the present invention but illustration the present invention.All features of discussing in the execution mode and its combination are not essential for the present invention.
Fig. 1 is the circuit diagram of the voltage generation circuit 100 of expression embodiment of the present invention.This voltage generation circuit 100 is according to reference voltage output voltage to be adjusted to three certain terminal voltage regulator, comprises current foldback circuit.
Fig. 4 is the block diagram of structure of the electronic installation 300 of the expression voltage generation circuit 100 that loaded Fig. 1.Electronic installation 300 for example is portable phone or PDA (Personal Digital Assistance), digital camera, CD player etc.Electronic installation 300 comprises battery 310, voltage generation circuit 100, load 320.Battery 310 for example is a lithium ion battery, the cell voltage about output 3～4V.This cell voltage Vbat is imported into the input terminal 102 of voltage generation circuit 100.Voltage generation circuit 100 is depressurized to the target voltage of regulation with the cell voltage Vbat of input, and with output voltage V out from lead-out terminal 104 outputs.On the lead-out terminal 104 of voltage generation circuit 100, connect load 320.Load 320 be with stable voltage as essential various circuit, in electronic installation 300, for example CPU, LED and motor, oscillator etc. are used as load and load.In load 320, flow through the output current Iout of voltage generation circuit 100.
Turn back to Fig. 1.Voltage generation circuit 100 comprises three terminals of input terminal 102, lead-out terminal 104, reference voltage terminal 106.Voltage that apply or that present on each terminal is called input voltage vin, output voltage V out, reference voltage V ref.Input voltage vin is the cell voltage Vbat of Fig. 4.
This voltage generation circuit 100 comprises adjuster the 10, the 1st testing circuit the 20, the 2nd testing circuit 30.
Input reference voltage Vref on the counter-rotating input terminal of operational amplifier 12.And on non-counter-rotating terminal, the feedback input has been carried out the R18/ that resistance is cut apart (R16+R18) output voltage V out doubly by resistance R 16, R18.The output of operational amplifier 12 is imported into the gate terminal of output transistor 14.
In adjuster 10, the grid voltage of 12 pairs of output transistors 14 of operational amplifier is regulated, so that the voltage of importing on non-counter-rotating input terminal and the counter-rotating input terminal equates.Therefore, output voltage V out is stabilized, so that Vout=Vref * (R16+R18)/the R18 establishment.To be called output current Iout by the electric current that output transistor 14 flows through load circuit.
The 1st testing circuit 20 comprises the 1st transistor the 22, the 1st resistance R 1, error amplifier 24, the constant pressure source 26 as P type MOSFET.The 1st transistor 22 is arranged in parallel with the output transistor 14 of adjuster 10, so that grid voltage is identical with source voltage, its current capacity specific output transistor 14 is little.Therefore, on the 1st transistor 22, flow through the electric current I corresponding 1 with output current Iout.The electric current I 1 that flows through in the 1st transistor 22 depends on the transistor size ratio of output transistor 14 and the 1st transistor 22, if the size of the 1st transistor 22 and output transistor 14 is than being M1, then on electric current I 1 and output current Iout, Iout=M1 * I1 sets up.
The 1st resistance R 1 is arranged between the drain terminal and earthing potential terminal of the 1st transistor 22, and electric current I 1 is transformed to voltage.That is, the 1st detection voltage V1 that presents on the 1st resistance R 1 is that the pairing current transformation of output current Iout that will flow through in the output transistor 14 is the voltage of voltage gained, and V1=I1 * R1=Iout/M1 * R1 sets up.
On error amplifier 24, import the 1st detection threshold voltage Vth that detects voltage V1 and generate by constant pressure source 26.This error amplifier 24 will be corresponding with output current Iout the 1st detect voltage V1 and compare with the detection threshold electric current I th1 corresponding threshold voltage Vth of the 1st testing circuit 20, when V1＞Vth, be judged as over-current state, and feed back, so that operational amplifier 12 is limited output currents.That is, the 1st testing circuit 20 is by comparing output current Iout and detection threshold electric current I th1, and the short-circuit condition of load circuit is detected.
In order to reduce the output current Iout of output transistor 14, if improve output transistor 14 gate terminal voltage and just can near input voltage vin.Under the situation of the common operational amplifier that constitutes by differential input level, amplifying stage, output stage, be connected to the amplifying stage of operational amplifier 12 by output with error amplifier 24, the grid voltage of output transistor 14 is changed forcibly, also can carry out the electric current restriction.
The feedback loop that exports operational amplifier 12 to that the 1st testing circuit 20 that below constitutes like that forms from voltage generation circuit 100.Therefore, error amplifier 24 is in order to ensure sufficient phase margin and improve the stability of circuit, and reduces the gain of feedback loop, band setting is got narrow.Owing to do not need to make error amplifier 24 high-speed responses,, can obtain to use the effect of operating time prolongation of the device of battery so reduce the current sinking of error amplifier 24 easily.
The 2nd testing circuit 30 comprises the 2nd transistor the 32, the 2nd resistance R 2, the detection transistor 34 as P type MOSFET.The 2nd transistor 32 is also same with the 1st transistor 22, is arranged in parallel with the output transistor 14 of adjuster 10, so that grid voltage is identical with source voltage.Therefore, in the 2nd transistor 32, flow through the electric current I corresponding 2 with output current Iout.If the size of the 2nd transistor 32 and output transistor 14 is than for M2, then for electric current I 2 and output current Iout, Iout=M2 * I2 sets up.
The 2nd resistance R 2 is arranged between the drain terminal and earthing potential terminal of the 2nd transistor 32, and electric current I 2 is transformed to voltage.That is, the 2nd detection voltage V2 that presents on the 2nd resistance R 2 also is the voltage that the output current Iout that flows through in the output transistor 14 is transformed to the voltage gained, and V2=I2 * R2=Iout/M2 * R2 sets up.
Detecting transistor 34 is bipolar transistors of NPN type, on its base terminal, is transfused to the 2nd and detects voltage V2.In the 2nd testing circuit 30, the 2nd Vf of up voltage forward that detects diode between voltage V2 and base-emitter that output current Iout is transformed to the voltage gained by this detection transistor 34 is compared, carry out the judgement of over-current state according to the conduction and cut-off that detects transistor 34.Up voltage Vf is the value about 0.7V in common silicon technology forward.
As mentioned above, V2=Iout/M2 * R2 sets up, and detects the 2nd and is judged to be over-current state when voltage V2 surpasses forward up voltage Vf.If the output current during this state counter-rotating is Ith2.The 2nd testing circuit 30 detects the short-circuit condition of load circuit by output current Iout and the detection threshold electric current I th2 that provides by Ith2=M2/R2 * Vf are compared.
At over-current state, when being Iout＞Ith2, V2＞Vf detects transistor 34 conductings.The collector terminal that detects transistor 34 also can similarly be connected to the amplifying stage of operational amplifier 12 with the 1st testing circuit 20.At this moment, when detecting transistor 34 conductings in over-current state, detect transistor 34 and introduce collector current from the amplifying stage of operational amplifier 12, institute can limit output current Iout so that its voltage changes also forcibly.
The 2nd testing circuit 30 that below constitutes like that has broadband because of the response speed with the high speed that is made of detection transistor 34.In the relation of detection threshold electric current I th1 in detection threshold electric current I th2 in the 2nd testing circuit 30 and the 1st testing circuit 20, become Rob Roy to set with Ith2＞Ith1.
The action of relevant above such voltage generation circuit that constitutes 100 is described according to Fig. 2 (a), Fig. 2 (b).Fig. 2 (a), Fig. 2 (b) are that expression is connected to the voltage under the situation of the load circuit short circuit on the voltage generation circuit 100, the time waveform of electric current.Be located at T0～T1 constantly, carry out common action, load circuit is short-circuited when moment T1.At first, the relevant situation that only makes 20 actions of the 1st testing circuit is described.
Shown in Fig. 2 (a), if load circuit is short-circuited when moment T1, then output voltage V out drops near 0V.At this moment Iout＜Ith1, so do not carry out the electric current restriction of the 1st testing circuit 20, adjuster 10 will generate the output voltage V out based on reference voltage V ref.Its result, shown in Fig. 2 (b), the output current Iout of output transistor 14 rises sharp.
When moment T2, if output current Iout reaches the detection threshold electric current I th1 of the 1st testing circuit 20, then error amplifier 24 beginning electric current restrictions.That is, the grid voltage of output transistor 14 is risen, output current Iout is reduced by operational amplifier 12 being applied feedback., the frequency band of feedback loop that comprises the 1st testing circuit 20 of this error amplifier 24 is set narrowly because of guaranteeing stability, and the response speed of the 1st testing circuit 20 is not near the rising that can follow the tracks of output current Iout.Therefore, shown in dotted line among Fig. 2 (b), in the 1st testing circuit 20, at V1＞Vth1, be Iout＞Ith1 after output current Iout ' continue to rise.Then, the feedback by error amplifier 24 is controlled operational amplifier 12, and the output current Iout ' of output transistor 14 reduces lentamente, approaches to detection threshold electric current I th1.
Like this, only undertaken by the 1st testing circuit 20 under the situation of electric current restriction, because of its restriction that detects responsiveness, output current Iout still rises after having surpassed detection threshold electric current I th1 and flows through big electric current, so be inadequate as circuit protection.
And under the situation of only carrying out the electric current restriction by the 2nd testing circuit 30, guarantee enough fast detection responsiveness because of the frequency that detects transistor 34 is wide, when output current Iout has surpassed detection threshold electric current I th2, apply feedback immediately, output current Iout is reduced., because phase margin fully do not guarantee, so circuit instability sometimes produces vibration.
Below, the action under the situation of using the 1st testing circuit 20 and the 2nd testing circuit 30 simultaneously is described.The waveform of the output current Iout of this moment is represented with solid line among Fig. 2 (b).
If load circuit is short-circuited when moment T1, output voltage V out step-down sharp then, output current Iout begins to rise sharp.If Iout＞Ith1 when moment T2 then detects over-current state by the 1st testing circuit 20, operational amplifier 12 is applied feedback, so that output current Iout reduces., as described above, because the detection responsiveness of the 1st testing circuit 20 is slow, so output current Iout continues to rise.
And then, when output current Iout rises to the detection threshold electric current I th2 of the 2nd testing circuit 30 when moment T3, detect transistor 34 conductings, operational amplifier 12 is applied feedback, so that output current Iout is limited.The detection responsiveness of the 2nd testing circuit 30 is near the variation that can fully follow the tracks of output current Iout, so output current Iout is limited to Ith2 immediately.Then, when moment T4, the feedback that detects the 1st slow testing circuit 20 of responsiveness begins to apply, and output current Iout begins to reduce lentamente, to reach the detection threshold electric current I th1 of the 1st testing circuit 20.Thus, compare, output current Iout is increased, and as soon as possible output current Iout is applied restriction with the situation of having only the 1st testing circuit 20.In addition, if output current Iout is littler than the detection threshold electric current I th2 of the 2nd testing circuit 30, V2＜Vf then, the detection transistor 34 of the 2nd testing circuit 30 ends, and feedback path is opened circuit, so the unsteadiness of circuit is eliminated.
As described above, according to the voltage generation circuit 100 of present embodiment, the rapid variation that can tackle output current Iout is carried out the electric current restriction and is not damaged the stability of circuit.Promptly, in the 1st testing circuit 20 of preferential design stability, under the situation that output current Iout rises sharp with the speed that can not follow the tracks of, the 2nd testing circuit 30 by preferential design action speed carries out the electric current restriction, then, after output current Iout was littler than the detection threshold electric current I th2 of the 2nd testing circuit 30, only the 1st testing circuit 20 carried out the electric current restriction.
Its result even circuit is unstable because of the feedback path of the 2nd testing circuit 30, owing to only switch to the electric current restriction of the 1st testing circuit 20, so do not damage the stability of circuit, can limit the rising of rapid output current Iout.
And, in the present embodiment, also can change detection threshold electric current I th1, the Ith2 of the 1st testing circuit 20 and the 2nd testing circuit 30 by the voltage corresponding with output voltage V out.Fig. 3 is the circuit diagram that is illustrated in the structure that is used to set the detection threshold electric current I th1 corresponding with output voltage V out in the 1st testing circuit 20.The 1st testing circuit 20 shown in Figure 3 also comprises the 3rd resistance R 3 and N type except the structure member of the 1st testing circuit 20 shown in Figure 1
MOSFETSwitching transistor SW3.
The setting of connecting with the 1st resistance R 1 of the 3rd resistance R 3, switching transistor SW3 and the 3rd resistance R 3 are arranged in parallel.
When output voltage V out was higher than the threshold voltage of the grid Vt of switching transistor SW3, switching transistor SW3 was switched on, and the 3rd resistance R 3 is by bypass, so only by the 1st resistance R 1, electric current is transformed to voltage.Therefore, the 1st detection voltage V1 provides by V1=I1 * R1=Iout/M1 * R1.
On the contrary, when output voltage V out is lower than the threshold voltage of the grid of switching transistor SW3,,, carry out current-voltage conversion so the 1st resistance R 1 and the 3rd resistance R 3 are connected directly because switching transistor SW3 ends.At this moment, the 1st detect voltage V1 by V1=I1 * R1=Iout/M1 * (R1+R3) provide.This means under the situation of switching transistor SW3 conducting, detection threshold electric current I th1 is set to Ith1=Vth * M1/R1, under the situation that switching transistor SW3 ends, detection threshold electric current I th1 is Ith1=Vth * M1/ (R1+R3), sets lowly during than conducting.
For example, establish the threshold voltage of the grid Vt that switching transistor SW3 goes up the N type MOSFET use and be 1V, detection threshold electric current I th1 is set lowly when Vout＜1V.Be short-circuited at load circuit, under the situation of Vout＜1V, be restricted to lower value by electric current with output transistor 14, useless current sinking when cutting down action usually, simultaneously can when short circuit, output current Iout be restricted to littler value, thereby suitably suppress the heating of output transistor 14.Also can similarly constitute about the 2nd testing circuit 30, the 2 resistance R 2.In addition, replace output voltage V out, according to output voltage V out voltage after partial, also can be to the conducting of switching transistor SW3, by controlling.
Above-mentioned execution mode is an illustration, it should be appreciated by those skilled in the art that they each structure member and the combination of each treatment process on various variation are arranged, and these variation are also within the scope of the invention.
In the present embodiment, situation about being short-circuited with the load circuit that is connected to lead-out terminal is the action that example has illustrated relevant current foldback circuit, but this circuit also works under the situation that load circuit is not short-circuited effectively.For example,, or connect under the situation of capacitor, when output voltage V out is improved, need make the capacitor charging as load circuit in parallel with load circuit.At this moment, under the situation that output voltage V out is improved sharp, flow into inrush current in the capacitor.The danger that this inrush current has the reliability to the capacitor that connects and other circuit elements to exert an influence sometimes.Under these circumstances, current foldback circuit of the present invention can be by the 1st testing circuit 20 and the 2nd testing circuit 30 and with output current Iout be suppressed to detection threshold electric current I th1, below the Ith2.
In the present embodiment, the situation that adopts current foldback circuit for three terminal linear regulators has been described, but has been not limited thereto.For example, also can be applied to booster circuit of having regulatory function etc.In this case, when the 1st and the 2nd testing circuit detects over-current state, also can apply the feedback that is used to limit electric current to pwm control circuit etc.That is, current foldback circuit of the present invention can be applied to limit the purposes of output current fully.
In the present embodiment, as output transistor 14 and the 1st transistor the 22, the 2nd transistor 32, with MOSFET is that example is illustrated, but also can use the transistor of other types such as bipolar transistor, their selection also can decide according to semiconductor fabrication process of the desired design standard of voltage generation circuit, use etc.On the contrary, for detecting transistor 34, also can use the transistor of MOSFET etc.
In the present embodiment, whole the integrating of the element that constitutes voltage generation circuit 100 also can be constituted its part with discrete parts.Which, decide just passable according to cost and occupied area etc. with partly integratedization.
In execution mode, illustrated voltage generation circuit 100 is loaded in by the situation on the battery-driven electronic installation 300, but be not limited thereto.For example, on the input terminal 102 of voltage generation circuit 100, replace battery 310, connect the power supply of AC/DC converter and DC/DC converter etc., also can make from the voltage of power supply output stable.Therefore, the voltage generation circuit 100 of execution mode can be widely used in the various uses that automobile and household electrical appliance etc. need carry out overcurrent protection.
Claims (7)
1. current foldback circuit; it is characterized in that; the situation to be output as over-current state from voltage generation circuit that comprises detects by the supervision electric current corresponding with the output current of this voltage generation circuit, and limits the 1st testing circuit, the 2nd testing circuit of described output current
Make the detection quick action of the detection responsiveness of described the 2nd testing circuit than described the 1st testing circuit, and, must be than the detection threshold electric current height of the over-current state of described the 1st testing circuit with the detection threshold current settings of the over-current state of described the 2nd testing circuit.
2. current foldback circuit as claimed in claim 1 is characterized in that, at least one of the detection threshold electric current of described the 1st testing circuit and the 2nd testing circuit is set lowly when the output voltage of described voltage generation circuit hangs down.
3. current foldback circuit as claimed in claim 1 or 2; it is characterized in that; described the 1st testing circuit, the 2nd testing circuit are connected in parallel with described voltage generation circuit respectively and will flow through the resistance that a terminal potential is fixed with the corresponding electric current of output current and be transformed to voltage; detect over-current state by relatively more corresponding voltage with separately detection threshold electric current
Described the 1st testing circuit comes comparative voltage by voltage comparator, limits the feedback of described output current,
Described the 2nd testing circuit will be input to by the voltage of described resistance conversion and detect transistorized control terminal, and with the corresponding over-current state that detects of the transistorized conduction and cut-off of described detection action, the electric current that flows through during according to conducting limits the feedback of described output current.
4. a voltage generation circuit is characterized in that, comprising: the adjuster circuit that comprises the operational amplifier of output transistor and the described output transistor of control; And the 1st testing circuit, the 2nd testing circuit,
Described the 1st testing circuit comprises:
The 1st transistor that is arranged in parallel with described output transistor;
The 1st resistance on the described the 1st transistorized current path is fixed and be arranged on to the voltage of one end; And
The voltage of voltage that presents on the other end of more described the 1st resistance and the 1st detection threshold electric current correspondence when the voltage that presents is high, limits the error amplifier of the feedback of output current to described operational amplifier on the other end of described the 1st resistance,
Described the 2nd testing circuit comprises:
The 2nd transistor that is arranged in parallel with described output transistor,
The 2nd resistance on the described the 2nd transistorized current path is fixed and be arranged on to the voltage of one end; And
The voltage that presents on the other end with described the 2nd resistance is input to control terminal, with the corresponding over-current state that detects of its conduction and cut-off action, and described operational amplifier is limited the detection transistor of the feedback of output current when detecting over-current state,
Must be with the detection threshold current settings of described the 2nd testing circuit than the detection threshold electric current height of described the 1st testing circuit.
5. an electronic installation is characterized in that, comprising:
Battery; And
The described voltage generation circuit of claim 4 with the voltage supply load of described battery.
6. electronic installation as claimed in claim 5 is characterized in that, also comprises the capacitor that is connected in parallel with described load.
7. an electronic installation is characterized in that, comprises;
Battery; And
Claim 1 or 2 described current foldback circuits that the electric current that flows into load from described battery is limited.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2004209109 | 2004-07-15 | ||
| JP209109/04 | 2004-07-15 | ||
| JP171174/05 | 2005-06-10 |
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| CN1722560A true CN1722560A (en) | 2006-01-18 |
| CN100550560C CN100550560C (en) | 2009-10-14 |
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| Application Number | Title | Priority Date | Filing Date |
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| CNB200510084805XA Expired - Fee Related CN100550560C (en) | 2004-07-15 | 2005-07-14 | Current foldback circuit |
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